What Rust crates are available for proxy management in web scraping?

In Rust, managing proxies for web scraping tasks is often an essential requirement to avoid IP bans or to scrape data from various geographical locations. While there isn't a vast ecosystem of Rust crates specifically designed for proxy management in web scraping compared to languages like Python, there are some crates available that can help you manage proxies and perform HTTP requests through them.

Here are a few Rust crates that can be useful for proxy management in web scraping:

• reqwest - While reqwest is primarily an HTTP client for Rust, it does support using proxies. You can configure reqwest to route your requests through a proxy server.

Here's how you can use a proxy with reqwest:

   use reqwest::Proxy;
   use std::error::Error;

   #[tokio::main]
   async fn main() -> Result<(), Box<dyn Error>> {
       let proxy = Proxy::all("http://your-proxy-server.com:port")?;
       let client = reqwest::Client::builder()
           .proxy(proxy)
           .build()?;

       let res = client.get("http://example.com")
           .send()
           .await?;

       println!("Status: {}", res.status());
       println!("Headers:\n{:#?}", res.headers());

       Ok(())
   }

• surf - surf is a lightweight, async HTTP client, which is built on top of http-client and supports middleware and proxies. You can set up a proxy using environment variables or by configuring the client directly.

Example with environment variable:

   export http_proxy=http://your-proxy-server.com:port
   export https_proxy=https://your-proxy-server.com:port

Directly configuring the client:

   use surf::http::Url;

   #[async_std::main]
   async fn main() -> surf::Result<()> {
       let proxy_url = Url::parse("http://your-proxy-server.com:port")?;
       let client = surf::client()
           .with(surf::middleware::Proxy::new(proxy_url));

       let mut res = client.get("https://example.com").await?;
       println!("Status: {}", res.status());
       Ok(())
   }

• hyper - hyper is a low-level HTTP implementation that you can use to make HTTP requests. You would need to manually handle the proxy connections, but it gives you more control over the request and response handling.

Since hyper is quite low-level, setting up a proxy involves manually creating and managing TcpStream connections and potentially using a TLS implementation like rustls or native-tls.

• tunnel - If you are looking for a way to tunnel HTTP requests through a proxy, the tunnel crate can be helpful. It's a lower-level crate that provides functionality to tunnel HTTP traffic over a proxy connection.

Here is an example of tunneling an HTTP request through a proxy with the tunnel crate:

use tunnel::Tunnel;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let proxy = "http://your-proxy-server.com:port";
    let destination = "http://example.com";
    let mut tunnel = Tunnel::new(proxy)?.connect(destination)?;
    tunnel.write_all(b"GET / HTTP/1.1\r\nHost: example.com\r\n\r\n")?;
    let mut response = String::new();
    tunnel.read_to_string(&mut response)?;
    println!("{}", response);

    Ok(())
}

When using these crates, ensure that you have the necessary permissions and that you are complying with the target website's terms of service and robots.txt file. Unauthorized use of proxies for web scraping can lead to legal issues and ethical concerns.